/* Copyright 2021, Gurobi Optimization, LLC */

/* This example formulates and solves the following simple MIP model:

     maximize    x +   y + 2 z
     subject to  x + 2 y + 3 z <= 4
                 x +   y       >= 1
                 x, y, z binary
*/
package gurobi_example;

import gurobi.GRB;
import gurobi.GRBEnv;
import gurobi.GRBException;
import gurobi.GRBLinExpr;
import gurobi.GRBModel;
import gurobi.GRBVar;

public class Mip1 {
    public static void main(String[] args) {
        try {

            // Create empty environment, set options, and start
            GRBEnv env = new GRBEnv(true);
            // env.set("logFile", "mip1.log");
            env.start();

            // Create empty model
            GRBModel model = new GRBModel(env);

            // Create variables
            GRBVar x = model.addVar(0.0, 1.0, 0.0, GRB.BINARY, "x");
            GRBVar y = model.addVar(0.0, 1.0, 0.0, GRB.BINARY, "y");
            GRBVar z = model.addVar(0.0, 1.0, 0.0, GRB.BINARY, "z");

            // Set objective: maximize x + y + 2 z
            GRBLinExpr expr = new GRBLinExpr();
            expr.addTerm(1.0, x);
            expr.addTerm(1.0, y);
            expr.addTerm(2.0, z);
            model.setObjective(expr, GRB.MAXIMIZE);

            // Add constraint: x + 2 y + 3 z <= 4
            expr = new GRBLinExpr();
            expr.addTerm(1.0, x);
            expr.addTerm(2.0, y);
            expr.addTerm(3.0, z);
            model.addConstr(expr, GRB.LESS_EQUAL, 4.0, "c0");

            // Add constraint: x + y >= 1
            expr = new GRBLinExpr();
            expr.addTerm(1.0, x);
            expr.addTerm(1.0, y);
            model.addConstr(expr, GRB.GREATER_EQUAL, 1.0, "c1");

            // Optimize model
            model.optimize();

            System.out.println(x.get(GRB.StringAttr.VarName) + " " + x.get(GRB.DoubleAttr.X));
            System.out.println(y.get(GRB.StringAttr.VarName) + " " + y.get(GRB.DoubleAttr.X));
            System.out.println(z.get(GRB.StringAttr.VarName) + " " + z.get(GRB.DoubleAttr.X));

            System.out.println("Obj: " + model.get(GRB.DoubleAttr.ObjVal));

            // Dispose of model and environment
            model.dispose();
            env.dispose();

        } catch (GRBException e) {
            System.out.println("Error code: " + e.getErrorCode() + ". " + e.getMessage());
        }
    }
}
